Karst rivers are of great interest for commercial fishing and aquaculture, yet they are quite vulnerable aquatic environments because the permeable karst rocks do not effectively filter out contaminants. To understand the current state of karst rivers water quality, we analysed the physico-chemical and microbiological parameters, focusing on antibiotic pollution and the emergence of antibiotic-resistant microbes of three such rivers in Croatia. Water quality varied between classes I and II across sampling sites, and the numbers of total coliforms, enterococci and heterotrophic bacteria varied substantially among sites. Swabs from fish gills, spleen, liver and kidneys were cultured and 94 isolates identified by MALDI-TOF mass spectrometry. The predominant genus was Aeromonas (42.5% of all identified isolates), known for its adaptability to polluted environments and its frequent association with antibiotic resistance. Of the selected Aeromonas isolates known as most pathogenic, half were resistant to at least three antibiotic categories. The Enterobacteriaceae family was represented by the greatest number of genera, most of which are pathogenic for humans and animals and are spoilage bacteria for fish. The results of this study highlight the extent of antibiotic contamination in aquatic environments and the increasing threat of pathogenic and spoilage bacteria in traditionally high-quality karst rivers.

中文翻译：

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东南黑海盆地（克罗地亚）喀斯特河水和鱼类的微生物质量评估，以及气单胞菌分离株的抗菌敏感性

喀斯特河流对商业捕鱼和水产养殖很感兴趣，但它们是非常脆弱的水生环境，因为可渗透的喀斯特岩石不能有效地过滤掉污染物。为了了解喀斯特河流水质的现状，我们分析了物理化学和微生物参数，重点关注克罗地亚三条此类河流的抗生素污染和抗生素抗性微生物的出现。不同采样点的 I 类和 II 类水质各不相同，并且总大肠菌群、肠球菌和异养细菌的数量因站点而异。培养了来自鱼鳃、脾脏、肝脏和肾脏的拭子，并通过 MALDI-TOF 质谱法鉴定了 94 个分离株。主要属是气单胞菌（占所有已鉴定分离株的 42.5%），以其对污染环境的适应性及其与抗生素耐药性的频繁联系而闻名。在被称为最具致病性的选定气​​单胞菌分离物中，一半对至少三种抗生素类别具有抗性。以肠杆菌科为代表的属数量最多，其中大部分对人和动物具有致病性，对鱼类来说是腐败菌。这项研究的结果突出了水生环境中抗生素污染的程度以及传统优质喀斯特河流中致病菌和腐败菌的威胁日益增加。以肠杆菌科为代表的属数量最多，其中大部分对人和动物具有致病性，对鱼类来说是腐败菌。这项研究的结果突出了水生环境中抗生素污染的程度以及传统优质喀斯特河流中致病菌和腐败菌的威胁日益增加。以肠杆菌科为代表的属数量最多，其中大部分对人和动物具有致病性，对鱼类来说是腐败菌。这项研究的结果突出了水生环境中抗生素污染的程度以及传统优质喀斯特河流中致病菌和腐败菌的威胁日益增加。